Fondant Icing Discolouring On Multiple Layers Of Fruit And Sponge

Does anyone have any advice about how to make sure the fondant icing remains the same shade. I reently made a four tier cake with two marzipanned fruit cakes and two butter-cream covered cakes,All were covered in ivory fondant, but the two fruit layers were much yellower than the other two. I also covered a dummy separtor with the same ivory fondant - this was a much cleaner colour - paler.

The overall effect was okay as it had lots of flowers etc, but if i wanted to do a simple design I would want the colours to look much more uniform and "clean". Any ideas?

I've seen in a cake decorating book that a fruit cake is usually first covered in marzipan (almond paste) and then with fondant. You first need to use a little marzipan and fill any small holes in the fruit cake so you get a nice smooth surface. Then you brush the fruit cake with some kind of glaze like apricot glaze and then cover it with marzipan (just like you would cover a cake with fondant). Then you need to make the marzipan tacky by brushing it with a little water. Leave the water on a for a couple of minutes to make sure the marzipan is tacky and the fondant will stick. Then cover the cake with fondant as usual. This way the fruit cake won't discolor the fondant. Hope this answers your question :)

Did you let the marzipan covered cake dry for at least 24 hours before covering it with fondant (I'm guessing a little longer would be even better)? That's also from the cake decorating book I have at home :) I guess you must've done this too :) If that's the case then coloring the buttercream (like kikiandkyle says ) might be the only way to go.